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Message-ID: <149148299794.3427.549144000807596903.stgit@warthog.procyon.org.uk>
Date: Thu, 06 Apr 2017 13:49:57 +0100
From: David Howells <dhowells@...hat.com>
To: ard.biesheuvel@...aro.org
Cc: dhowells@...hat.com, matthew.garrett@...ula.com,
linux-security-module@...r.kernel.org, linux-efi@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: [PATCH 1/5] efi: Move the x86 secure boot switch to generic code
Move the switch-statement in x86's setup_arch() that inteprets the
secure_boot boot parameter to generic code.
Suggested-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
Signed-off-by: David Howells <dhowells@...hat.com>
---
arch/x86/kernel/setup.c | 14 +-------------
drivers/firmware/efi/Kconfig | 23 +++++++++++++++++++++++
drivers/firmware/efi/Makefile | 3 ++-
drivers/firmware/efi/secure_boot.c | 34 ++++++++++++++++++++++++++++++++++
include/linux/efi.h | 6 ++++++
5 files changed, 66 insertions(+), 14 deletions(-)
create mode 100644 drivers/firmware/efi/secure_boot.c
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 4bf0c8926a1c..b89979ffa6e5 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -1178,19 +1178,7 @@ void __init setup_arch(char **cmdline_p)
/* Allocate bigger log buffer */
setup_log_buf(1);
- if (efi_enabled(EFI_BOOT)) {
- switch (boot_params.secure_boot) {
- case efi_secureboot_mode_disabled:
- pr_info("Secure boot disabled\n");
- break;
- case efi_secureboot_mode_enabled:
- pr_info("Secure boot enabled\n");
- break;
- default:
- pr_info("Secure boot could not be determined\n");
- break;
- }
- }
+ efi_set_secure_boot(boot_params.secure_boot);
reserve_initrd();
diff --git a/drivers/firmware/efi/Kconfig b/drivers/firmware/efi/Kconfig
index 2e78b0b96d74..4b902ffbfcf4 100644
--- a/drivers/firmware/efi/Kconfig
+++ b/drivers/firmware/efi/Kconfig
@@ -84,6 +84,29 @@ config EFI_PARAMS_FROM_FDT
config EFI_RUNTIME_WRAPPERS
bool
+config EFI_SECURE_BOOT
+ bool "Support UEFI Secure Boot and lock down the kernel in secure boot mode"
+ default n
+ help
+ UEFI Secure Boot provides a mechanism for ensuring that the firmware
+ will only load signed bootloaders and kernels. Secure boot mode may
+ be determined from EFI variables provided by the BIOS if not
+ indicated by the boot parameters.
+
+ Enabling this option turns on support for UEFI secure boot in the
+ kernel. This will result in various kernel facilities being locked
+ away from userspace if the kernel detects that it has been booted in
+ secure boot mode. If it hasn't been booted in secure boot mode, or
+ this cannot be determined, the lock down doesn't occur.
+
+ The kernel facilities that get locked down include:
+ - Viewing or changing the kernel's memory
+ - Directly accessing ioports
+ - Directly specifying ioports and other hardware parameters to drivers
+ - Storing the kernel image unencrypted for hibernation
+ - Loading unsigned modules
+ - Kexec'ing unsigned images
+
config EFI_ARMSTUB
bool
diff --git a/drivers/firmware/efi/Makefile b/drivers/firmware/efi/Makefile
index ad67342313ed..65969f840685 100644
--- a/drivers/firmware/efi/Makefile
+++ b/drivers/firmware/efi/Makefile
@@ -22,7 +22,8 @@ obj-$(CONFIG_EFI_FAKE_MEMMAP) += fake_mem.o
obj-$(CONFIG_EFI_BOOTLOADER_CONTROL) += efibc.o
obj-$(CONFIG_EFI_TEST) += test/
obj-$(CONFIG_EFI_DEV_PATH_PARSER) += dev-path-parser.o
-obj-$(CONFIG_APPLE_PROPERTIES) += apple-properties.o
+obj-$(CONFIG_EFI_SECURE_BOOT) += secure_boot.o
+obj-$(CONFIG_APPLE_PROPERTIES) += apple-properties.oo
arm-obj-$(CONFIG_EFI) := arm-init.o arm-runtime.o
obj-$(CONFIG_ARM) += $(arm-obj-y)
diff --git a/drivers/firmware/efi/secure_boot.c b/drivers/firmware/efi/secure_boot.c
new file mode 100644
index 000000000000..cf5bccae15e8
--- /dev/null
+++ b/drivers/firmware/efi/secure_boot.c
@@ -0,0 +1,34 @@
+/* Core kernel secure boot support.
+ *
+ * Copyright (C) 2017 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@...hat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public Licence
+ * as published by the Free Software Foundation; either version
+ * 2 of the Licence, or (at your option) any later version.
+ */
+
+#include <linux/efi.h>
+#include <linux/kernel.h>
+#include <linux/printk.h>
+
+/*
+ * Decide what to do when UEFI secure boot mode is enabled.
+ */
+void __init efi_set_secure_boot(enum efi_secureboot_mode mode)
+{
+ if (efi_enabled(EFI_BOOT)) {
+ switch (mode) {
+ case efi_secureboot_mode_disabled:
+ pr_info("Secure boot disabled\n");
+ break;
+ case efi_secureboot_mode_enabled:
+ pr_info("Secure boot enabled\n");
+ break;
+ default:
+ pr_info("Secure boot could not be determined\n");
+ break;
+ }
+ }
+}
diff --git a/include/linux/efi.h b/include/linux/efi.h
index 94d34e0be24f..d8938a780290 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -1488,6 +1488,12 @@ enum efi_secureboot_mode {
};
enum efi_secureboot_mode efi_get_secureboot(efi_system_table_t *sys_table);
+#ifdef CONFIG_EFI_SECURE_BOOT
+void __init efi_set_secure_boot(enum efi_secureboot_mode mode);
+#else
+static inline void efi_set_secure_boot(enum efi_secureboot_mode mode) {}
+#endif
+
/*
* Arch code can implement the following three template macros, avoiding
* reptition for the void/non-void return cases of {__,}efi_call_virt():
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